Lipomatous metaplasia prolongs repolarization and increases repolarization dispersion within post-infarct ventricular tachycardia circuit cites.

AIMS: Post-infarct myocardium contains viable corridors traversing scar or lipomatous metaplasia (LM). Ventricular tachycardia (VT) circuitry has been separately reported to associate with corridors that traverse LM and with repolarization heterogeneity. We examined the association of corridor activation recovery interval (ARI) and ARI dispersion with surrounding tissue type. METHODS AND RESULTS: The cohort included 33 post-infarct patients from the prospective Intra-Myocardial Fat Deposition and Ventricular Tachycardia in Cardiomyopathy (INFINITY) study. We co-registered scar and corridors from late gadolinium enhanced magnetic resonance, and LM from computed tomography with intracardiac electrogram locations. Activation recovery interval was calculated during sinus or ventricular pacing, as the time interval from the minimum derivative within the QRS to the maximum derivative within the T-wave on unipolar electrograms. Regional ARI dispersion was defined as the standard deviation (SD) of ARI per AHA segment (ARISD). Lipomatous metaplasia exhibited higher ARI than scar [325 (interquartile range 270-392) vs. 313 (255-374), P < 0.001]. Corridors critical to VT re-entry were more likely to traverse through or near LM and displayed prolonged ARI compared with non-critical corridors [355 (319-397) vs. 302 (279-333) ms, P < 0.001]. ARISD was more closely associated with LM than with scar (likelihood ratio χ2 50 vs. 12, and 4.2-unit vs. 0.9-unit increase in 0.01*Log(ARISD) per 1 cm2 increase per AHA segment). Additionally, LM and scar exhibited interaction (P < 0.001) in their association with ARISD. CONCLUSION: Lipomatous metaplasia is closely associated with prolonged local action potential duration of corridors and ARI dispersion, which may facilitate the propensity of VT circuit re-entry.

Epidemic modeling with heterogeneity and social diffusion.

We propose and analyze a family of epidemiological models that extend the classic Susceptible-Infectious-Recovered/Removed (SIR)-like framework to account for dynamic heterogeneity in infection risk. The family of models takes the form of a system of reaction-diffusion equations given populations structured by heterogeneous susceptibility to infection. These models describe the evolution of population-level macroscopic quantities S, I, R as in the classical case coupled with a microscopic variable f, giving the distribution of individual behavior in terms of exposure to contagion in the population of susceptibles. The reaction terms represent the impact of sculpting the distribution of susceptibles by the infection process. The diffusion and drift terms that appear in a Fokker-Planck type equation represent the impact of behavior change both during and in the absence of an epidemic. We first study the mathematical foundations of this system of reaction-diffusion equations and prove a number of its properties. In particular, we show that the system will converge back to the unique equilibrium distribution after an epidemic outbreak. We then derive a simpler system by seeking self-similar solutions to the reaction-diffusion equations in the case of Gaussian profiles. Notably, these self-similar solutions lead to a system of ordinary differential equations including classic SIR-like compartments and a new feature: the average risk level in the remaining susceptible population. We show that the simplified system exhibits a rich dynamical structure during epidemics, including plateaus, shoulders, rebounds and oscillations. Finally, we offer perspectives and caveats on ways that this family of models can help interpret the non-canonical dynamics of emerging infectious diseases, including COVID-19.

Prognostic Value of Nonischemic Ringlike Left Ventricular Scar in Patients With Apparently Idiopathic Nonsustained Ventricular Arrhythmias.

BACKGROUND: Left ventricular (LV) scar on late gadolinium enhancement (LGE) cardiac magnetic resonance has been correlated with life-threatening arrhythmic events in patients with apparently idiopathic ventricular arrhythmias (VAs). We investigated the prognostic significance of a specific LV-LGE phenotype characterized by a ringlike pattern of fibrosis. METHODS: A total of 686 patients with apparently idiopathic nonsustained VA underwent contrast-enhanced cardiac magnetic resonance. A ringlike pattern of LV scar was defined as LV subepicardial/midmyocardial LGE involving at least 3 contiguous segments in the same short-axis slice. The end point of the study was time to the composite outcome of all-cause death, resuscitated cardiac arrest because of ventricular fibrillation or hemodynamically unstable ventricular tachycardia and appropriate implantable cardioverter defibrillator therapy. RESULTS: A total of 28 patients (4%) had a ringlike pattern of scar (group A), 78 (11%) had a non-ringlike pattern (group B), and 580 (85%) had normal cardiac magnetic resonance with no LGE (group C). Group A patients were younger compared with groups B and C (median age, 40 vs 52 vs 45 years; P<0.01), more frequently men (96% vs 82% vs 55%; P<0.01), with a higher prevalence of family history of sudden cardiac death or cardiomyopathy (39% vs 14% vs 6%; P<0.01) and more frequent history of unexplained syncope (18% vs 9% vs 3%; P<0.01). All patients in group A showed VA with a right bundle-branch block morphology versus 69% in group B and 21% in group C (P<0.01). Multifocal VAs were observed in 46% of group A patients compared with 26% of group B and 4% of group C (P<0.01). After a median follow-up of 61 months (range, 34-84 months), the composite outcome occurred in 14 patients (50.0%) in group A versus 15 (19.0%) in group B and 2 (0.3%) in group C (P<0.01). After multivariable adjustment, the presence of LGE with ringlike pattern remained independently associated with increased risk of the composite end point (hazard ratio, 68.98 [95% CI, 14.67-324.39], P<0.01). CONCLUSIONS: In patients with apparently idiopathic nonsustained VA, nonischemic LV scar with a ringlike pattern is associated with malignant arrhythmic events.

Esophageal luminal temperature rise during atrial fibrillation ablation is associated with lower radiofrequency electrode distance and baseline impedance.

INTRODUCTION: Esophageal injury during atrial fibrillation (AF) ablation is a life-threatening complication. We sought to measure the association of esophageal temperature attenuation with radiofrequency (RF) electrode impedance, contact force, and distance from the esophagus. METHODS: The retrospective study cohort included 35 patients with mean age 64 ± 10 years, of whom 74.3% were male, and 40% had persistent AF. All patients had undergone preprocedural cardiac magnetic resonance (CMR) followed by AF ablation with luminal esophageal temperature monitoring. Lesion locations were co-registered with CMR image segmentations of left atrial and esophageal anatomy. Luminal esophageal temperature, time matched RF lesion data, and ablation distance from the nearest esophageal location were collected as panel data. RESULTS: Luminal esophageal temperature changes corresponding to 3667 distinct lesions, delivered with mean power 27.9 ± 5.5 W over a mean duration of 22.2 ± 10.5 s were analyzed. In multivariable analyses, clustered per patient, examining posterior wall lesions only, and adjusted for lesion power and duration as set by the operator, lesion distance from the esophagus (-0.003°C/mm, p < .001), and baseline impedance (-0.015°C/Ω, p < .001) were associated with changes in luminal esophageal temperature. CONCLUSION: Esophageal luminal temperature rises are associated with shorter lesion distance from esophagus and lower baseline impedance during RF lesion delivery. When procedural strategy requires RF delivery near the esophagus, selection of sites with higher baseline impedance may improve safety.

Endogenous T1ρ cardiovascular magnetic resonance in hypertrophic cardiomyopathy.

BACKGROUND: Hypertrophic cardiomyopathy (HCM) is characterized by increased left ventricular wall thickness, cardiomyocyte hypertrophy, and fibrosis. Adverse cardiac risk characterization has been performed using late gadolinium enhancement (LGE), native T1, and extracellular volume (ECV). Relaxation time constants are affected by background field inhomogeneity. T1ρ utilizes a spin-lock pulse to decrease the effect of unwanted relaxation. The objective of this study was to study T1ρ as compared to T1, ECV, and LGE in HCM patients. METHODS: HCM patients were recruited as part of the Novel Markers of Prognosis in Hypertrophic Cardiomyopathy study, and healthy controls were matched for comparison. In addition to cardiac functional imaging, subjects underwent T1 and T1ρ cardiovascular magnetic resonance imaging at short-axis positions at 1.5T. Subjects received gadolinium and underwent LGE imaging 15-20 min after injection covering the entire heart. Corresponding basal and mid short axis LGE slices were selected for comparison with T1 and T1ρ. Full-width half-maximum thresholding was used to determine the percent enhancement area in each LGE-positive slice by LGE, T1, and T1ρ. Two clinicians independently reviewed LGE images for presence or absence of enhancement. If in agreement, the image was labeled positive (LGE + +) or negative (LGE --); otherwise, the image was labeled equivocal (LGE + -). RESULTS: In 40 HCM patients and 10 controls, T1 percent enhancement area (Spearman's rho = 0.61, p < 1e-5) and T1ρ percent enhancement area (Spearman's rho = 0.48, p < 0.001e-3) correlated with LGE percent enhancement area. T1 and T1ρ percent enhancement areas were also correlated (Spearman's rho = 0.28, p = 0.047). For both T1 and T1ρ, HCM patients demonstrated significantly longer relaxation times compared to controls in each LGE category (p < 0.001 for all). HCM patients also showed significantly higher ECV compared to controls in each LGE category (p < 0.01 for all), and LGE -- slices had lower ECV than LGE + + (p = 0.01). CONCLUSIONS: Hyperenhancement areas as measured by T1ρ and LGE are moderately correlated. T1, T1ρ, and ECV were elevated in HCM patients compared to controls, irrespective of the presence of LGE. These findings warrant additional studies to investigate the prognostic utility of T1ρ imaging in the evaluation of HCM patients.

Canadian Association of Radiologists White Paper on De-Identification of Medical Imaging: Part 1, General Principles.

The application of big data, radiomics, machine learning, and artificial intelligence (AI) algorithms in radiology requires access to large data sets containing personal health information. Because machine learning projects often require collaboration between different sites or data transfer to a third party, precautions are required to safeguard patient privacy. Safety measures are required to prevent inadvertent access to and transfer of identifiable information. The Canadian Association of Radiologists (CAR) is the national voice of radiology committed to promoting the highest standards in patient-centered imaging, lifelong learning, and research. The CAR has created an AI Ethical and Legal standing committee with the mandate to guide the medical imaging community in terms of best practices in data management, access to health care data, de-identification, and accountability practices. Part 1 of this article will inform CAR members on principles of de-identification, pseudonymization, encryption, direct and indirect identifiers, k-anonymization, risks of reidentification, implementations, data set release models, and validation of AI algorithms, with a view to developing appropriate standards to safeguard patient information effectively.

Canadian Association of Radiologists White Paper on De-identification of Medical Imaging: Part 2, Practical Considerations.

The application of big data, radiomics, machine learning, and artificial intelligence (AI) algorithms in radiology requires access to large data sets containing personal health information. Because machine learning projects often require collaboration between different sites or data transfer to a third party, precautions are required to safeguard patient privacy. Safety measures are required to prevent inadvertent access to and transfer of identifiable information. The Canadian Association of Radiologists (CAR) is the national voice of radiology committed to promoting the highest standards in patient-centered imaging, lifelong learning, and research. The CAR has created an AI Ethical and Legal standing committee with the mandate to guide the medical imaging community in terms of best practices in data management, access to health care data, de-identification, and accountability practices. Part 2 of this article will inform CAR members on the practical aspects of medical imaging de-identification, strengths and limitations of de-identification approaches, list of de-identification software and tools available, and perspectives on future directions.

Association of septal late gadolinium enhancement on cardiac magnetic resonance with ventricular tachycardia ablation targets in nonischemic cardiomyopathy.

BACKGROUND: Ablation of septal substrate-associated ventricular tachycardia (VT) in patients with nonischemic cardiomyopathy (NICM) is challenging. We sought to standardize the characterization of septal substrates on late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) and to examine the association of that substrate with VT exit and isthmus sites on invasive mapping. METHODS: LGE-CMR was performed before electroanatomic mapping and ablation for VT in 20 NICM patients. LGE extent and distribution were quantified using myocardial signal-intensity Z scores (SI-Z). The SI-Z thresholds correlating to previously validated voltage thresholds, for abnormal tissue and dense scar were defined. RESULTS: Bipolar and unipolar (electrogram) voltage amplitude measurements from the LV and RV were negatively associated with SI-Z from LGE-CMR imaging (p < .05). SI-Z thresholds for appropriate CMR identification of septal substrates were determined to be greater than -.15 for border zone and greater than .03 for a dense scar. Among all patients, 34 critical VT sites were identified with SI-Z distribution in the range of -.97 to .06. Thirty (88.2%) critical sites were located in the dense LGE, 1 (2.9%) in the border zone, and 3 (8.9%) in healthy tissue but within 7 mm of LGE. Of note, critical VT sites were all located at the basal septum close to valves (distance to aortic valve: 17.5 ± 31.2 mm, mitral valve: 21.2 ± 8.7 mm) in nonsarcoidosis cases. CONCLUSIONS: Critical sites of septal VT in NICM patients are predominantly in the CMR defined dense scar when using standardized signal-intensity thresholds.

Association of scar distribution with epicardial electrograms and surface ventricular tachycardia QRS duration in nonischemic cardiomyopathy.

INTRODUCTION: The association of late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) with epicardial and surface ventricular tachycardia (VT) electrogram features, in nonischemic cardiomyopathy (NICM), is unknown. We sought to define the association of LGE and viable wall thickness with epicardial electrogram features and exit site paced QRS duration in patients with NICM. METHODS: A total of 19 patients (age 53.5 ± 11.5 years) with NICM (ejection fraction 40.2 ± 13.2%) underwent CMR before VT ablation. LGE transmurality was quantified on CMR and coregistered with 2294 endocardial and 2724 epicardial map points. RESULTS: Both bipolar and unipolar voltage were associated with transmural signal intensity on CMR. Longer electrogram duration and fractionated potentials were associated with increased LGE transmurality, but late potentials or local abnormal ventricular activity were more prevalent in nontransmural versus transmural LGE regions (p < .05). Of all critical VT sites, 19% were located adjacent to regions with LGE but normal bipolar and unipolar voltage. Exit site QRS duration was affected by LGE transmurality and intramural scar location, but not by wall thickness, at the impulse origin. CONCLUSIONS: In patients with NICM and VT, LGE is associated with epicardial electrogram features and may predict critical VT sites. Additionally, exit site QRS duration is affected by LGE transmurality and intramural location at the impulse origin or exit.

DICOM Images Have Been Hacked! Now What?

OBJECTIVE. As health care moves into a new era of increasing information vulnerability, radiologists should understand that they may be using systems that are exposed to altered data or data that contain malicious elements. This article explains the vulnerabilities of DICOM images and discusses requirements to properly secure these images from cyberattacks. CONCLUSION. There is an important need to properly secure DICOM images from attacks and tampering. The solutions described in this article will go a long way to achieving this goal.

Utility of ripple mapping for identification of slow conduction channels during ventricular tachycardia ablation in the setting of arrhythmogenic right ventricular cardiomyopathy.

BACKGROUND: Ripple mapping displays every deflection of a bipolar electrogram and enables the visualization of conduction channels (RMCC) within postinfarction ventricular scar to guide ventricular tachycardia (VT) ablation. The utility of RMCC identification for facilitation of VT ablation in the setting of arrhythmogenic right ventricular cardiomyopathy (ARVC) has not been described. OBJECTIVE: We sought to (a) identify the slow conduction channels in the endocardial/epicardial scar by ripple mapping and (b) retrospectively analyze whether the elimination of RMCC is associated with improved VT-free survival, in ARVC patients. METHODS: High-density right ventricular endocardial and epicardial electrograms were collected using the CARTO 3 system in sinus rhythm or ventricular pacing and reviewed for RMCC. Low-voltage zones and abnormal myocardium in the epicardium were identified by using standardized late-gadolinium-enhanced (LGE) magnetic resonance imaging (MRI) signal intensity (SI) z-scores. RESULTS: A cohort of 20 ARVC patients that had undergone simultaneous high-density right ventricular endocardial and epicardial electrogram mapping was identified (age 44 ± 13 years). Epicardial scar, defined as bipolar voltage less than 1.0 mV, occupied 47.6% (interquartile range [IQR], 30.9-63.7) of the total epicardial surface area and was larger than endocardial scar, defined as bipolar voltage less than 1.5 mV, which occupied 11.2% (IQR, 4.2 ± 17.8) of the endocardium (P < 0.01). A median 1.5 RMCC, defined as continuous corridors of sequential late activation within scar, were identified per patient (IQR, 1-3), most of which were epicardial. The median ratio of RMCC ablated was 1 (IQR, 0.6-1). During a median follow-up of 44 months (IQR, 11-49), the ratio of RMCC ablated was associated with freedom from recurrent VT (hazard ratio, 0.01; P = 0.049). Among nine patients with adequate MRI, 73% of RMCC were localized in LGE regions, 24% were adjacent to an area with LGE, and 3% were in regions without LGE. CONCLUSION: Slow conduction channels within endocardial or epicardial ARVC scar were delineated clearly by ripple mapping and corresponded to critical isthmus sites during entrainment. Complete elimination of RMCC was associated with freedom from VT.

Lack of Growth of Small (≤2 mm Feeding Artery) Untreated Pulmonary Arteriovenous Malformations in Patients with Hereditary Hemorrhagic Telangiectasia.

PURPOSE: To assess pulmonary arteriovenous malformation (PAVM) growth among patients with untreated PAVMs using imaging from long-term follow-up per hereditary hemorrhagic telangiectasia international guidelines. MATERIALS AND METHODS: Analysis included 88 untreated PAVMs from 21 patients (6 male;15 female; mean age at presentation 47 y; range, 12-68 y). Two CT studies with the longest interval between were evaluated (mean 8.4 y; median 8.8 y; range, 3.1-14.1 y). Measurement of feeding artery diameter and anteroposterior (AP) and mediolateral (ML) sac dimensions for each PAVM was performed separately by 2 radiologists blinded to patient and CT order. Statistical analysis was performed to determine change in size between earliest and follow-up imaging. RESULTS: Mean feeding artery diameter, AP sac dimension, and ML sac dimension were 1.4 mm (range, 0.8-3.7 mm), 4.3 mm (range, 2.1-11.1 mm), and 4.1 mm (range, 1.8-9.2 mm) on earliest imaging and 1.4 mm (range, 0.9-2.6 mm), 4.5 mm (range, 2.2-12.2 mm), and 4.3 mm (range, 2.0-9.6 mm) on follow-up. Model-based mean analysis showed no statistically significant change in dimension of any variable between earliest and follow-up imaging. Secondary analysis including age also found no statistically significant difference (feeding diameter, P = .09; AP sac dimension, P = .9; ML sac dimension, P = .1). Analysis including time between measurements found no significant relationship between change in variables and time (feeding artery diameter, P = .4; AP sac dimension, P = .3; ML sac dimension, P = .06). CONCLUSIONS: Untreated PAVMs grew slowly, if at all, in a near-decade span, and any demonstrated growth was minimal. These findings challenge the current recommendation of 3- to 5-year CT follow-up.

Unipolar voltage mapping criteria for right ventricular septum: Influence of the aortic root.

INTRODUCTION: Unipolar voltage mapping through its wider "field of view" can identify substrate deeper to the endocardium on the right ventricular (RV) free wall and left ventricle. The reference value(s) for normal endocardial (ENDO) unipolar voltage (UNI) for the septal aspect of the right ventricle (RV) and the effect of the aortic root that is directly opposed to the posterior septal plane of the RV outflow tract (RVOT) have not been established. METHODS AND RESULTS: We performed detailed (185 ± 70, range 127-342 points) RV ENDO UNI maps in 9 patients without structural heart disease; 6 had magnetic resonance (MR) imaging; 5 were males; the mean age was 49 ± 11 years. For MR analysis, the location of the aortic root was defined and its effect on unipolar voltage determined. The UNI voltage on posterior RVOT was lower (mean 6.56 ± 2.33 mV, 95% CI 6.08-7.05), compared to the rest of the septal aspect of RV (mean 8.33 ± 2.34 mV, P < 0.001, 95% CI 7.84-8.84). MR analysis confirmed that the lowest voltage region was opposite to MR-defined aortic root. Using a cutoff for UNI abnormality of 6.0 mV for the posterior aspect of the RVOT opposite to the aortic root and 7.5 mV for the rest of the septal aspect of the RV, there was no confluent area of unipolar abnormality in any patient. CONCLUSION: We defined normal ENDO UNI cutoffs as 7.5 mV for the septal aspect of the RV with adjustment to 6.0 mV over the posterior RVOT opposite to the aortic root.

Prognostic role of serial quantitative evaluation of 18F-fluorodeoxyglucose uptake by PET/CT in patients with cardiac sarcoidosis presenting with ventricular tachycardia.

BACKGROUND: Positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) has shown to be useful in diagnosis, staging and monitoring of cardiac sarcoidosis (CS) but its interpretation is not standardized. OBJECTIVES: We sought to investigate the clinical impact of serial quantitative FDG uptake analysis in patients with CS presenting with ventricular tachycardia (VT) treated by catheter ablation (CA). METHODS: We followed 20 patients (51 ± 9 years, 70% males) with CS and VT who underwent CA, with 92 serial FDG-PET scans (3-10 per patient). Myocardial FDG-avid lesions were quantified using three parameters: maximum standardized uptake value (SUVmax), partial-volume corrected mean standardized uptake value (SUVmean) and partial-volume corrected volume-intensity product [lesion metabolic activity (LMA)]. The volume-intensity product of the entire heart [global cardiac metabolic activity (gCMA)] and the background cardiac metabolic activity (bCMA: difference between gCMA and LMA) were also calculated. The primary end-point was the occurrence of major adverse cardiac events (MACE), including death, heart transplant, hospitalization for heart failure and implantable cardioverter defibrillator (ICD) appropriate interventions. Evolution of echocardiographic parameters over follow-up was also assessed. RESULTS: During a median follow-up of 35 (20-66) months, 18 MACE (1 death, 2 heart transplants, 12 ICD appropriate interventions, 3 hospitalizations) occurred in 12 (60%) patients. At univariable analysis, lack of PET improvement (defined by decrease in LMA of at least 25%) was the only variable associated with cardiac events during follow-up. In particular, non-responders had a 20-fold higher risk of MACE at follow-up (HR 18.96, 95% CI 2.26-159.27; p = 0.007). Moreover, a significant linear inverse relationship was observed between changes in LMA and changes in left ventricular ejection fraction over follow-up (ß = -20.11; p = 0.003). CONCLUSIONS: In patients with CS and VT, temporal change in FDG uptake evaluated by a quantitative approach is associated with parallel change in systolic function. Moreover, reduction in FDG uptake is strongly associated with fewer MACE at long-term follow-up.

Contact electroanatomic mapping derived voltage criteria for characterizing left atrial scar in patients undergoing ablation for atrial fibrillation.

BACKGROUND: Criteria have not been established for identifying LA scar using electroanatomic mapping (EAM). It is also unclear if voltage criteria using EAM may assist in identifying areas of pulmonary vein (PV) reconnection in patients undergoing repeat AF ablation. OBJECTIVES: To characterize left atrial (LA) voltage in patients undergoing atrial fibrillation (AF) ablation. METHODS: An LA shell was created and bipolar voltage amplitude (in mV) at each point was measured. The shell was divided into 8 regions. Bipolar voltage values lower than the amplitude of 95% of sampled points was used as the upper cutoff value. Delayed enhancement (DE) cardiac magnetic resonance imaging (CMRI) sequences were performed to validate voltage cutoffs. RESULTS: Twenty patients participated. A mean of 141 ± 12 points constituted the LA map that was created during sinus rhythm (SR). In patients undergoing initial AF ablation, mean bipolar LA voltage was 1.44 ± 1.27 mV. In patients undergoing repeat AF ablation, scar along the posterior wall and LA-PV junction was identified using a voltage cutoff <0.2 mV, whereas a cutoff <0.45 mV best identified scar at other locations. This voltage range (0.2-0.45 mV) was useful to identify areas of reconnection around the PVs. On DE CMRI, a bipolar voltage cutoff of 0.27 mV performed best for delineating scar (sensitivity: 90%, specificity: 83%). CONCLUSIONS: In patients undergoing AF ablation, EAM derived LA bipolar voltage shows regional variation. For maps acquired during SR, a voltage range of 0.2-0.45 mV can accurately demarcate LA scar distribution. This can be helpful in identifying PV reconnection in patients undergoing repeat AF ablation.

Lipomatous Metaplasia Is Associated With Ventricular Tachycardia Recurrence Following Ablation in Patients With Nonischemic Cardiomyopathy.

BACKGROUND: Ventricular tachycardia (VT) recurrence rates remain high following ablation among patients with nonischemic cardiomyopathy (NICM). OBJECTIVES: This study sought to define the prevalence of lipomatous metaplasia (LM) in patients with NICM and VT and its association with postablation VT recurrence. METHODS: From patients who had ablation of left ventricular VT, we retrospectively identified 113 consecutive NICM patients with preprocedural contrast-enhanced cardiac computed tomography (CECT), from which LM was segmented. Nested within this cohort were 62 patients that prospectively underwent CECT and cardiac magnetic resonance from which myocardial border zone and dense late gadolinium enhancement (LGE) were segmented. A control arm of 30 NICM patients without VT with CECT was identified. RESULTS: LM was identified among 57% of control patients without VT vs 83% of patients without VT recurrence and 100% of patients with VT recurrence following ablation. In multivariable analyses, LM extent was the only independent predictor of VT recurrence, with an adjusted HR per 1-g LM increase of 1.1 (P < 0.001). Patients with LM extent ≥2.5 g had 4.9-fold higher hazard of VT recurrence than those with LM <2.5 g (P < 0.001). In the nested cohort with 32 VT recurrences, LM extent was independently associated with VT recurrence after adjustment for border zone and LGE extent (HR per 1 g increase: 1.1; P = 0.036). CONCLUSIONS: Myocardial LM is prevalent in patients with NICM of a variety of etiologies, and its extent is associated with postablation VT recurrence independent of the degree of fibrosis.

ACR Appropriateness Criteria ® imaging of mesenteric ischemia.

Mesenteric ischemia is a rare disease associated with high morbidity and mortality. Acute mesenteric ischemia is most commonly secondary to embolism followed by arterial thrombosis, nonocclusive ischemia, and less commonly venous thrombosis. Chronic mesenteric ischemia is almost always caused by atherosclerotic disease, with rare causes including fibromuscular dysplasia and vasculitis. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances where evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment. Patients with mesenteric ischemia usually present with nonspecific abdominal symptoms and laboratory findings. This document evaluates and rates the appropriateness of imaging to evaluate patients with clinically suspected mesenteric ischemia. While catheter-based angiography has been considered the reference standard and enables diagnosis and treatment, advances in computed tomography have made it a first-line test in many patients because it is a fast, widely available, and noninvasive study. Abdominal radiographs and ultrasound have a limited role in diagnosing mesenteric ischemia but are commonly the first ordered tests in patients with abdominal pain and may diagnose more common pathologies.

Noninvasive Assessment of Lipomatous Metaplasia as a Substrate for Ventricular Tachycardia in Chronic Infarct.

Myocardial lipomatous metaplasia (LM) has been increasingly reported in patients with prior myocardial infarction. Cardiac magnetic resonance and cardiac contrast-enhanced computed tomography have been used to noninvasively detect and quantify myocardial LM in postinfarct patients, and may provide useful information for understanding cardiac mechanics, arrhythmia susceptibility, and prognosis. This review aims to summarize the advantages and disadvantages, clinical applications, and imaging features of different cardiac magnetic resonance sequences and cardiac contrast-enhanced computed tomography for LM detection and quantification. We also briefly summarize LM prevalence in different cohorts of postinfarct patients and review the clinical utility of cardiac imaging in exploring myocardial LM as an arrhythmogenic substrate in patients with prior myocardial infarction.

Correlation of myocardial strain by CMR-feature tracking with substrate abnormalities detected by electro-anatomical mapping in patients with nonischemic cardiomyopathy.

BACKGROUND: Late gadolinium enhancement (LGE) detected by cardiac MRI (CMR) has low correlation with low voltage zones (LVZs) detected by electroanatomical mapping (EAM). We aim to study correlation of myocardial strain by CMR- Feature Tracking (FT) alongside LGE with LVZs detected by EAM. METHODS: Nineteen consecutive CMRs of patients with EAM were analyzed offline by CMR-FT. Peak value of circumferential strain (CS), longitudinal strain (LS), and LGE was measured in each segment of the left ventricle (17-segment model). The percentage of myocardial segments with CS and LS > -17% was determined. Percentage area of LGE-scar was calculated. Global and segment-wise bipolar and unipolar voltage was collected. Percentage area of bipolar LVZ (<1.5 mV) and unipolar LVZ (<8.3 mV) was calculated. RESULTS: Mean age was 62±11 years. Mean LVEF was 37±13%. Mean global CS was -11.8±5%. Mean global LS was -11.2±4%. LGE-scar was noted in 74% of the patients. Mean percentage area of LGE-scar was 5%. There was significant correlation between percentage abnormality detected by LS with percentage bipolar LVZ (r = +0.5, p = 0.03) and combined percentage CS+LS abnormality with percentage unipolar LVZ (r = +0.5, p = 0.02). Per-unit increase in CS increased the percentage area of unipolar LVZ by 2.09 (p = 0.07) and per-unit increase in LS increased the percentage area of unipolar LVZ by 2.49 (p = 0.06). The concordance rates between CS and LS to localize segments with bipolar/unipolar LVZ were 79% and 95% compared to 63% with LGE. CONCLUSIONS: Myocardial strain detected by CMR-FT has a better correlation with electrical low voltage zones than the conventional LGE.